Biological information which is currently increasing is difficult to rapidly process using existing laboratory analysis systems. According to this tendency, biological detection systems for the elucidation of life phenomena, the development of new drugs and the diagnosis of diseases are, for purposes of analyzing samples in smaller amounts in a rapid and accurate manner for a short time based on microfluidics, being developed in the forms of micro-Total Analysis Systems (μ-TAS) and lab-on-a-chip. Because most biological samples to be analyzed are present in solution, technology for transferring liquid samples is considered a particularly important factor.
Microfluidics is a field of study in which the flow of microfluids is controlled and which studies and develops a key technology on which the commercial use of the micro-total analysis systems and lab-on-a-chips is based. The micro-total analysis system is a system in which chemical and biological experiments and assays comprising a number of experimental steps and reactions are comprehensively carried out in one unit present on one testing bench. Such a micro-total analysis system comprises a sample collection area, a microfluidic circuit, a detector and a controller for controlling them.
Also, the term “lab-on-a-chip” refers to a “laboratory-in-a-chip” or “laboratory-on-a-chip” technology. In this technology, microchannels of nanoliter or sub-nanoliter volumes are made using a material such as plastic, glass, silicon or the like, and liquid samples in amounts as small as a few nanoliters are moved through the microchannels, such that existing experiments or studies can be rapidly carried out. The realization of said micro-total analysis system or lab-on-a-chip capable of rapidly carrying out analysis for rapidly increasing biological information can be effectively achieved by effecting a combination with suitable methods for analyzing biological molecules.
Technology for separating particles using the magnetic susceptibility of particles is recently receiving a great deal of attention. The magnetic susceptibility of a material refers to the extent to which the material will become magnetized when placed in a magnetic field. Magnetic materials can be divided into diamagnetic materials, paramagnetic materials and ferromagnetic materials according to their magnetic susceptibility.
A prior magnetophoresis technique utilizes the phenomenon in which particles exposed to a magnetic field move simply by the force of the magnetic field. In the prior magnetophoresis technique, an insignificant difference in magnetic susceptibility between particles cannot be distinguished, and if there is a certain variation in the size of particles, the analytical errors will become larger, thus making it difficult to separate fine particles and analyze the magnetic properties thereof.
                                          F            _                    mag                =                                            V              ⁡                              (                                                      χ                    p                                    -                                      χ                    surr                                                  )                                                    μ              0                                ⁢                      B            ⁡                          (                              ∇                B                            )                                                          [                  Math          ⁢                                          ⁢          Figure          ⁢                                          ⁢          1                ]            wherein Vindicates the volume of particles, χp and χsurr indicate the magnetic susceptibilities of particles and the surrounding fluid, respectively, B(∇B) represents a magnetic flux density gradient, and μ0 indicates the permeability in vacuum. According to the above equation, in the prior magnetophoresis technique, the parameter values are set according to the behavior of particles, and thus magnetophoretic particle separation has been used to separate magnetic particles showing a very great difference in size or magnetic susceptibility therebetween.
Korean Patent Registration No. 10-0695743 discloses a technique for separating biomolecular particles using magnetophoresis, which has a construction in which the behavior of a particle to which a magnetic field has been applied is continuously reinforced by the difference in magnetic susceptibility between it and the surrounding solution. However, this construction can be applied only to the case in which the difference in magnetic susceptibility between particles is great. In addition, because the volume of particles can change, there is difficulty in separating fine particles and analyzing the magnetic properties thereof.
FIG. 1 shows a prior system for separating fine particles using magnetophoresis. As shown in FIG. 1, the prior system for separating fine particles using magnetophoresis comprises an inlet 101 for introducing fine particles and a sample fluid, a microfluidic channel 102 through which the introduced fluid and fine particles pass, and a magnetic energy source 103 for applying a magnetic force in a direction perpendicular to the microfluidic channel 102. Herein, the moving pathway of the introduced fine particles is changed from the central portion of the channel by the magnetic force of the magnetic energy source 103, and the fine particles can be separated according to the degree of the pathway change. However, the fine particle-separating system can effectively separate fine particles only when the difference in magnetic susceptibility between the fine particles is great.
Also, technology for separating nanoparticles based on the difference in magnetic susceptibility between ferromagnetic nanoparticles and nanotubes has been studied (a research paper by Joo H. Kang and Je-Kyun Park; unpublished). This technology has a construction in which particles are separated from each other by observing the change in moving pathway of the particles caused by the difference in magnetic susceptibility between the particles. However, this technology can be applied only when the difference in magnetic susceptibility between particles is great.
Systems for separating fine particles using magnetic forces, which were developed to date, could be applied only when the volume of particles was large or the difference in magnetic susceptibility between particles was great. However, the industrial demand for the separation of fine particles, such as minerals, synthetic polymers, cells, proteins and nucleic acids, is increasing.